problem with uml project

Posted 07 November 2012 - 07:32 AM

I need to know what I'm doing wrong in this diagram. I'm new to UML language and having a problem with this task:

To improve the management of meetings related to their staff a certain firm requested the development of a system to schedule and cancel meetings. The staff consists of:
- Workers, which are alocated in one of the firm departments;
-Managers, who are workers of a department responsible for the managing of the department;
-Directors, who are not alocated to any department and are responsible for the general administration of the firm.
The system will manage the staff schedule to facilitate the management of meetings among the different staff teams. The events managed by the system will be the following:
-Work Group, event chosen by a worker and that involves just one worker of his department;
-Inner Meeting, which is scheduled by a department manager and that involves one or more workers of his department;
-Director's meeting, scheduled by a director and that involves one or more managers.
When a scheduling of some event( certain place, date and people involved) is requested the system must provide date and hour options to this event. In the case the time provided is not satisfactory the system must have an option to cancel the previous arrangements to allow the scheduling of another event. Also, the system must allow the view of the schedule of any requested worker.